Sensitivity enhancement of surface plasmon resonance immunosensing by antibody–antigen coupling

A method of the sensitivity enhancement for the wavelength modulation surface plasmon resonance immunosensing is described using an antibody–antigen coupling assay. The sensor surface was prepared by self-assembling monolayer (SAM), and regenerated by rising with citrate buffer. The human factor B (Bf) showed a good response in the concentration range 0.50–20.00 μg/ml in direct assay. However, Bf had a better response in the concentration range 0.05–20.00 μg/ml by using competitive immunoreactions between antibody immobilized on the sensor film and antibody in the solution. When the antibody–antigen coupling assay was used, the lowest concentration of Bf that could be detected is 10-fold lower than by direct assay. With the same antibody–antigen coupling method, fibronectin (FN) could be detected in the concentration range 0.25–20.00 μg/ml. The lowest detectable concentration is eight-fold lower than by direct assay. The sensor chip could be reusable in the determination of antigen for more than 10 assay cycles without significant decrease of the activity.